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Background

Athletes exposed to extreme training loads such as those that occur during multiple-game
tournaments, two a day practices, or sudden increases in volume are prone to overreaching.
Beta-hydoxy-beta-methylbutyrate (HMB) is thought to increase regenerative capacity
following high intensity exercise. However, to date, its effects on muscle damage,
hormonal status, and performance during overreaching have yet to be investigated.
Therefore the purpose of this investigation was to determine the effects of HMB free
acid (HMB-FA) supplementation on indices of muscle damage, strength, power, and cortisol
following a 2-week overreaching cycle.

Methods

Twenty resistance trained males aged 21.3 ± 1.9 years were recruited for the study
and randomly assigned to consume 3 g per day of HMB-FA (combined with food-grade orange
flavors and sweeteners) or a placebo (food-grade orange flavors and sweeteners). All
subjects were placed on a diet consisting of 25 % protein, 50 % carbohydrates, and
25 % fat by a registered dietician who specialized in sport (RD, LDN, CISSN). Seventy-two
hours prior to the overreaching phase subjects were tested for baseline measures of
creatine kinase (CK), cortisol, Wingate power and strength on the squat, bench press,
and deadlift. Following, all subjects participated in a 2-week high volume resistance-training
cycle. Each Monday through Thursday, subjects performed 3 maximal sets of 8-12 repetitions
and 60-90 seconds rest of squats, leg press, bench press, deadlifts, pull-ups, military
press, bent over rows, barbell curls and extensions. On Friday subjects were given
three 1-RM attempts on the squat, bench press, and deadlift for a total of 9 maximal
working sets, followed by power testing on the Wingate on Saturday. A 2 X 3 (Group
X time (weeks 0, 1, and 2)) repeated measures ANOVA was used to assess any main effects.
If main effects were found LSD post hoc tests were incorporated to determine where
differences were located.

Results

Significant group X time effects were found for CK, which relative to baseline values
(256.1 ± 28.3 U/L) increased at weeks 1 (493.8 ± 36.3 U/L) and 2 (533.4 ± 49.0 U/L)
in the placebo group, but not the HMB group (p<0.05). There were also group X time
effects for strength of the squat, bench press, and deadlift, which decreased during
weeks 1 and 2 (ranging from -5.6 to -7.1% across strength measures) in the placebo
group, but not the HMB group (p<0.05). A group x time effect was found for Wingate
peak power, which relative to baseline values (991.0 ± 60.1 watts) was lower at weeks
1 (924.6 ± 58.3 watts) and 2 (946.6 ± 59.1 watts) in the placebo group but not the
HMB group. Finally there were group X time effects for cortisol, which relative to
baseline (19.3 ± 1.4 ug/dl) increased in both weeks 1 (22.1 ± 1.4 ug/dl) and 2 (23.7
± 1.0 ug/dl) in the placebo group, but not the HMB group (p<0.05).

Conclusions

These results suggest HMB-FA given over a 2-week high volume, low recovery training
cycle prevents overreaching, as well as the characteristic rise in serum stress hormones
and serum indices of muscle damage.